Tuesday, March 31, 2015, 5:12 p.m.

Deep water thwarts robot sub's 1st search for jet

PERTH, Australia — A robotic submarine hunting for the missing Malaysian jet aborted its first mission after only six hours, surfacing with no new clues when it exceeded its maximum depth along the floor of the Indian Ocean, officials said Tuesday.

Search crews sent the U.S. Navy's Bluefin 21 into the depths Monday to begin scouring the seabed for the missing Malaysia Airlines Boeing 777 after failing for six days to detect any new signals believed to be coming from its black boxes.

But the 16-hour mission was cut short when the unmanned sub, which is programmed to hover 100 feet above the seabed, entered a patch that was deeper than its maximum depth of 15,000 feet, the search coordination center and the U.S. Navy said.

A built-in safety feature returned the Bluefin to the surface and it was not damaged, they said.

The data collected by the sub was later analyzed and no sign of the missing plane was found, the U.S. Navy said. Crews were shifting the Bluefin's search area away from the deepest water and were hoping to send it back on another mission later Tuesday.

Search authorities had known the primary search area for Flight 370 was near the limit of the Bluefin's dive capabilities. Deeper-diving submersibles have been evaluated, but none is yet available to help.